The probe was the result of a lawsuit filed by eBay in December 1999 against Bidder's Edge, which allowed customers to simultaneously track a number of auction sites.

Soon after the case was filed, the Department of Justice's antitrust division asked for documents relating to the suit and eBay's licensing deals with other auction aggregators.

"The division has closed its investigation without taking action against us," eBay said in its annual filing March 25 with the Securities and Exchange Commission.

eBay last year had 42.4 million registered users and more than 423 million listings. Transactions via the site were valued at $9.3 billion.

In its lawsuit, eBay alleged that tracking software from Bidder's Edge was not only trespassing its site, but also burdening the servers. Bidder's Edge contended that the site was public since it was shaped that way by consumers' auction listings and bids.

A court in May temporarily restrained Bidder's Edge from trawling eBay with its robots. And earlier this month Bidder's Edge settled with eBay for an undisclosed sum.